Balloon catheter with non-deployable stent

ABSTRACT

An angioplasty balloon including a non-deployable stent to prevent or reduce the potential for slippage of the inflated balloon with respect to the vessel wall being treated. The balloon includes a non-deployable stent that is adapted to be secured to the balloon or angioplasty balloon catheter. The stent has a proximal end, a distal end, and at least three radially-spaced struts, each strut connecting the proximal end to the distal end and having one or more bends that allow expansion of the strut to accommodate the inflation of the balloon. The stent is made of a material so that the stent collapses upon deflation or the balloon.

BACKGROUND OF THE INVENTION

When a balloon used for percutaneous transluminal angioplasty (PTA) orpercutaneous transluminal coronary angioplasty (PTCA) is inflated andforced into contact with the plaque, the balloon can have a tendency tomove or slip longitudinally in relation to the lesion or the vessel wallbeing treated.

Cutting balloons (atherotomy) have recently shown clinical efficacy inpreventing the reoccurrence of some types of restenosis (specificallycalcified lesions and in-stent restenosis). The cutting balloon is acoronary dilatation catheter with 3 to 4 atherotomes (microsurgicalblades) bonded longitudinally on the balloon surface. As the cuttingballoon is inflated, the atherotomes move radially and open the occludedartery by incising and compressing the arterial plaque in a controlledmanner. An additional advantage of the cutting balloon is that itmaintains its position during inflation by using the metal blades on theexternal surface of the balloon to penetrate into the tissue and preventthe balloon from moving.

Accordingly, it is the principal objective of the present invention toprovide a PTA or PTCA balloon that, like a cutting balloon, has areduced potential of slippage when inflated in a vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an inflated angioplasty balloonincorporating a non-deployable stent according to the present invention.

FIG. 2 is a plan view of the inflated angioplasty balloon andnon-deployable stent of FIG. 1.

FIG. 3 is a perspective view of the non-deployable stent in its expandedcondition, as shown in FIG. 1, with the angioplasty balloon removed soas to more clearly show the stent.

FIG. 4 is a plan view of the non-deployable stent of FIG. 3.

FIG. 5 is a perspective view of an alternate embodiment of thenon-deployable stent associated with an angioplasty balloon that has alonger working length than the angioplasty balloon shown in FIGS. 1 and2.

FIG. 6 is an engineering drawing showing, in plan view, the layout of anon-deployable stent adapted to be used with an angioplasty balloon of20 mm in length. (All dimensions shown in the drawing are in inches.)

FIG. 7 is a perspective view of an inflated angioplasty balloonincorporating an alternative embodiment of a non-deployable stent whichdoes not include any connecting elements between the struts intermediatethe ends of the balloon.

FIG. 8 is a perspective view of the non-deployable stent shown in FIG.7, with the angioplasty balloon removed so as to more clearly show thestent.

FIGS. 9 and 10 are perspective views similar to FIGS. 1, 5, and 7showing a further embodiment of the invention.

FIG. 11 is a perspective view of a further embodiment of the presentinvention showing the balloon and non-deployable stent in conjunctionwith a catheter.

DESCRIPTION

The non-deployable stent of the present invention may be used inconjunction with a conventional balloon catheter. A PTA or PTCA catheter(dilatation catheter) may be a coaxial catheter with inner and outermembers comprising a guide wire lumen and a balloon inflation lumen,respectively. Each member can have up to 3 layers and can be reinforcedwith braids. The proximal end of the catheter has a luer hub forconnecting an inflation means, and a strain relief tube extends distallya short distance from the luer hub. The distal ends of the outer andinner members may include a taper. The catheter shaft is built usingconventional materials and processes. A catheter having multi-durometertubing with variable stiffness technology is also a possibility. Thecatheter should be compatible with a 6 F guide catheter. Optionally, thecatheter may be a multi-lumen design.

The balloon 1 may be made of either nylon or nylon copolymer (compliant,non-puncture) or PET (high pressure, non-compliant) with a urethanecoating to provide tackiness. The balloon may be a multi-layered balloonwith a non-compliant inner layer to a most compliant outer layer. Forexample, a inner most layer of PET, which provides a higher pressureballoon, surrounded by an outer layer of nylon, which provides a morepuncture-resistant surface. The balloon may be from 1.5-12 mm indiameter (1.5-4 mm for coronary and 4-12 mm for peripheral vessels) and15-60 mm in length (15-40 mm for coronary and up to 60 mm for peripheralvessels). The balloon inflation pressure will be from 8-20 atmospheres,depending on the wall thickness of the balloon. When inflated, theballoon ends or necks are cone-shaped.

In keeping with the invention, the balloon is provided with a Nitinol(NiTi) structure, generally designated 2, that incorporates bends forboth radial and longitudinal expansion of the Nitinol structure 2 inresponse to longitudinal and radial expansion of the balloon duringinflation, so that the Nitinol structure 2 maintains the balloon in itsintended position during inflation. This Nitinol structure 2 can bedescribed as a non-deployable or temporary stent that provides for bothcontrolled cracking of vessel occlusion and gripping of vessel wallduring an angioplasty procedure. The Nitonol structure 2 comprises alaser cut hypo tube that expands upon inflation of the balloon, butcollapses upon deflation of the balloon because of the super-elasticproperties of the Nitinol material, rather than remain expanded in thedeployed condition, as would stents in general.

The Nitinol structure or non-deployable stent 2 has a proximal end 3, adistal end 4, and, therebetween, anywhere from 3-12 struts or wires 5(depending on balloon size—but most likely 3-4 struts) with a pattern ofradial and longitudinal bends. The use of laser cutting in connectionwith stent manufacture is well known (See, e.g., Meridan et al. U.S.Pat. No. 5,994,667), as is the use of the super-elastic nickel—titaniumalloy Nitinol (see e.g., Huang et al. U.S. Pat. No. 6,312,459).

As seen in FIGS. 1-4, each end of the linear, longitudinally alignedfour struts 5 has a sinusoidal bend 6 that allows the laser cut hypotube to expand longitudinally when the balloon 1 is inflated. The linearlength of the sinusoidal bends 6 is sized to accommodate thelongitudinal expansion of the balloon 1 due to inflation. The strut orwire 5 cross sectional shape can be round, triangular or rectangular.Preferred diameter of the struts 5 ranges from 0.003 to 0.010 inch.

At the longitudinal center of the hypo tube, a U-shaped circumferentialconnector 7 joins each strut 5 to its adjacent strut. As best seen inFIGS. 3 and 4, the U-shaped connectors 7 are on opposing sides of thecentral radial axis. The distal end 4 of the hypo tube is adhered to thedistal neck of the balloon or the distal end of the catheter shaft, andthe proximal end 3 of the hypo tube is either attached to the proximalneck of the balloon or to the proximal end of the catheter shaft. Thestruts 5 may be attached to the working region of the balloon 1 toassist the hypo tube in staying with the balloon as it inflates anddeflates, and an adhesive, such as a cyanoacrylate adhesive, may be usedto tack the struts down onto balloon at various points.

Catheter shafts to which the balloon and laser cut hypo tube areattached can have diameters ranging from 2.5 F to 8 F, and the distalend may be tapered and slightly less in diameter than the proximal end.

In FIG. 6, the dimensions of the laser cut hypo tube are for use with a3 mm (0.118 in) diameter by 20 mm length balloon. The circumference of a3 mm balloon is nD=3.14(3 mm)=9.42 mm or 0.37 in. As can be readilyappreciated, the total length of all U-shaped connectors 7 (up and back)must be greater than the circumference of the inflated balloon 1. Thelength of each U-shaped connector 7 (up and back), may be calculatedusing the following equation:

$\frac{\Pi\; d}{n},$where d is the diameter of the inflated balloon and n is the number ofstruts. The total length of the U-shaped bends (up and back) must exceedthis length.

The resulting number is divided by 2 to get the length which eachup-and-back side of the U-shaped connector should exceed. For example:for a 3 mm balloon compatible, laser-cut hypo tube with four struts, thelength of each U-shaped connector (up and back) is 0.37 inch divided by4=0.0925 in. Further divide by 2 and to get 0.04625 in. This is thelength that each side of the U-shaped connector must exceed.

There is also one or more sets of U-shaped connectors 7 in between thesinusoidal bends 6. The set includes one U-shaped connector for eachstrut (3 struts—a set of 3 U-shaped connectors; 4 struts—a set of 4U-shaped connector; and so on). The number of U-shaped connector setsdepends on the length of the balloon and thus, the length of the lasercut hypo tube. For a 20 mm length balloon, there is one set of U-shapedconnectors spaced 10 mm from the end (at the halfway point along lengthof balloon). For a 40 mm length balloon, there are three sets ofU-shaped connectors spaced in 10 mm increments (the first set is spaced10 mm from one end; the second set is spaced 10 mm from first set; andthe third set is spaced 10 mm from each the second set and the otherend). The equation for number of sets of U-shaped connectors.

${\frac{L}{10} - 1},$where L=length of balloon in mm. Other embodiments, such as those shownin FIGS. 7 and 8, have linear, longitudinally aligned struts 5 withbends 6 at each end which do not incorporate the intermediate U-shapedconnectors.

1. An angioplasty balloon catheter comprising: a catheter shaft carryingan inflatable/deflatable balloon having a proximal end and a distal end;and a non-deployable radially expansible stent comprising a hypo tubedisposed over the balloon and comprising a proximal end; a distal end;and at least three longitudinally aligned, radially-spaced struts,wherein each strut extends from the proximal end to the distal end andprior to radial expansion has one or more bends that allow longitudinalexpansion of the strut to accommodate radial expansion of the stent uponinflation of the balloon; wherein the distal end of the hypo tube isattached to the distal end of the catheter shaft and the proximal end ofthe tube is attached to the proximal end of the catheter shaft and thestent is made of a material having a memory so that the stent radiallycollapses and the struts longitudinally shorten upon deflation of theballoon.
 2. The angioplasty balloon of claim 1 wherein the stent is madeof an alloy of nickel and titanium.
 3. The angioplasty balloon of claim1 wherein the struts of the stent have a diameter of from 0.003″ to0.010″.
 4. The angioplasty balloon of claim 1 wherein the bends in thestruts of the stent are sinusoidal.
 5. The angioplasty balloon of claim1 wherein the hypo tube is laser cut.
 6. The angioplasty balloon ofclaim 1 wherein the stent is secured to the balloon by an adhesive. 7.The angioplasty balloon of claim 6 wherein the adhesive is acyanoacrylate.
 8. The angioplasty balloon of claim 1 wherein the strutsof the stent are connected to each other intermediate the proximal endand distal end by connectors that include a bend which allowslongitudinal expansion of the connectors to accommodate radial expansionof the balloon.
 9. The stent of claim 8 wherein the connectors in thestruts comprise sinusoidal bends.